How do cancel abilities work with unrevealed crew? The specific example I’m thinking of involves crew with the Eternal keyword encountering a ship with the “one ship/crew within S can’t use its ability that turn” ability. If the person knows I typically use Eternal, can they just call it out as cancelled on a hunch? Or does it have to be revealed by in-game means to be cancelled?
You can’t cancel a facedown crew, even if you do know what it is. You have to wait until it’s revealed before it can be targeted.
With a facedown Eternal crew, the only way to cancel it (the first time, at least), is for the canceller to be within range of the sinking ship at the moment it would sink, which is when the Eternal crew would have to be revealed.
There’s some metagaming opportunity there in deciding whether to reveal an Eternal crew that you know would get cancelled immediately, to leave the opponent guessing about a facedown crew on some other ship, but whether you reveal and get cancelled or choose not to reveal, either way you’re going to lose the first ship.